Method for processing separate containers of biological fluid

ABSTRACT

Processes and systems for combining multiple units of a biological fluid in independent containers into a single container are disclosed.

This application is a continuation of application Ser. No. 08/107,033,filed Aug. 17, 1993, now U.S. Pat. No. 5,364,526 which is a continuationof Ser. No. 07/795,480, filed on Nov. 21, 1991 abandoned.

TECHNICAL FIELD

This invention relates to a system, apparatus, and method for processingseparate containers of biological fluid.

BACKGROUND OF THE INVENTION

The development of plastic blood collection bags in the 1960'sfacilitated the separation of donated whole blood into its variouscomponents, thereby making a platelet concentrate (PC) available as atransfusion product. A typical unit of random-donor PC is about 50 ml,and is typically produced from a unit of whole blood, which is about 450ml in United States practice, by differential sedimentation.

The need for specific blood components is growing rapidly as thetherapeutic administration of these components increases. The net resultis twofold: biological fluids are increasingly important, and the needto maximize yield has increased. Thus, any amount that is retained inthe processing system, or is recovered but is not viable andphysiologically active, represents a potentially significant loss. Whilethe failure to maximize yield is a serious concern with respect to allblood components, it is particularly applicable to the production of PC,since typical procedures for processing platelet containing solutionssuch as PC fail to efficiently maximize platelet recovery.

Maximizing recovery of platelets or a platelet concentrate afterprocessing may be adversely affected in several ways. For example,platelets are notorious for being "sticky", an expression reflecting thetendency of platelets suspended in blood plasma to adhere to anynon-physiological surface (e.g., the surfaces of the components of asystem for processing biological fluid) to which they are exposed. Undermany circumstances, they also adhere strongly to each other.

As detailed in U.S. Pat. No. 4,880,548, which discloses methods anddevices for leucocyte depleting blood components including PC, therewill be substantial contact between platelets and the internal surfacesof the leucocyte depletion device. It is therefore desirable that theleucocyte depletion device should minimize platelet loss due to thatcontact and should not adversely affect, platelet viability orphysiological activity.

This problem is magnified when multiple units of platelet containingsolutions are pooled or processed. When multiple Units of PC from randomdonors are pooled for transfusion into a patient, some of the fluid istrapped or retained in the individual collection and processingassemblies, collectively representing a significant loss if the highlyvaluable fluid can not be recovered.

In view of this, there is a growing need for a system and method foreconomically and efficiently processing a biological fluid, such as aplatelet containing solution, that will not only pool large amounts(e.g. multiple units) of the fluid, but will also leucocyte deplete thefluid and maximize the recovery of platelets.

DEFINITIONS

The following definitions are used in reference to the invention:

(A) Biological Fluid: Biological fluid includes any treated or untreatedfluid associated with living organisms, particularly blood, includingwhole blood, warm or cold blood, and stored or fresh blood; treatedblood, such as blood diluted with a physiological solution, includingbut not limited to saline, nutrient, and/or anticoagulant solutions; oneor more blood components., such as platelet concentrate (PC),platelet-rich plasma (PRP), platelet-free plasma, platelet-poor plasma,plasma, or packed red cells (PRC); analogous blood products derived fromblood or a blood component or derived from bone marrow; red cellsseparated from plasma and resuspended in physiological fluid; andplatelets separated from plasma and resuspended in physiological fluid.The biological fluid may include leucocytes, or may be treated to removeleucocytes. As used herein, biological fluid refers to the componentsdescribed above, and to similar blood products obtained by other meansand with similar properties.

(B) Unit of PC or platelets: As used herein, a "unit" is defined in thecontext of United States practice, and a unit of PC or of platelets inphysiological fluid or plasma, is the quantity derived from one unit ofwhole blood. Typically, the volume of a unit varies. Multiple units ofplatelets may be pooled or combined, typically by combining four or moreunits.

(C) Porous medium: A porous medium is one through which one or morebiological fluids pass. The porous medium for use with biological fluidsmay be formed from any natural or synthetic fiber or from a porous orpermeable membrane (or from other materials of similar surface area andpore size) compatible with biological fluid (e.g., blood or a bloodcomponent). The surface of the fibers or membrane may be unmodified ormay be modified to achieve a desired property. For example, the mediummay be subjected to gas plasma treatment, preferably in order to reduceplatelet adhesion.

Although the porous medium may remain untreated, the fibers or membraneare preferably treated in order to reduce or eliminate plateletadherence to the medium. Any treatment which reduces or eliminatesplatelet adhesion is included within the scope of the present invention.For example, the fibers may be surface modified as disclosed in U.S.Pat. 4,880,548, in order to increase the critical wetting surfacetension (CWST) of the fibers and to be less adherent of platelets.Defined in terms of CWST, a preferred range of CWST for a porous mediumaccording to the invention is above about 70 dynes/cm, more preferablyabove about 90 dynes/cm.

The porous medium may be pre-formed, multilayered, and/or may be treatedto modify the fiber surfaces either before or after forming the fibrouslay-up. The porous medium may be configured in any suitable fashion,such as a flat sheet, a corrugated sheet, a web, hollow fibers, or amembrane.

SUMMARY OF THE INVENTION

Processes and systems according to the invention include a manifoldassembly for combining multiple units of a biological fluid inindependent, containers into a single container. Processes and systemsaccording to the invention may also include a leucocyte depletionassembly.

Additionally, processes ,and systems according to the invention mayinclude a gas inlet and/or a gas outlet that maximizes the recovery of abiological fluid that may Be entrapped or retained during processing;the processes and systems may also include a drip chamber that collectsgas and/or controls the rate of flow of a biological fluid through thesystem.

The processes and systems of the present invention provide for increasedyield of a biological fluid, since valuable fluid that would normally beretained in various elements of a biological fluid processing system maynow be recovered. The present invention also provides for reducedprocessing time and operator labor.

BRIEF DESCRIPTION OF THE DRAWINGS

The FIGURE is an embodiment of a biological fluid processing systemcomprising a manifold assembly according to the invention.

SPECIFIC DESCRIPTION OF THE INVENTION

In accordance with the present invention, units of biological fluid,particularly PC, which are in separate source containers, are passedthrough a biological fluid processing system which maximizes recovery ofthe biological fluid into a single receiving container. The processingsystem may also include a leucocyte depletion assembly that isinterposed between the source containers and the receiving container.

An exemplary biological fluid processing system is shown in the FIGURE.Manifold assembly 100 may include containers 20, each suitable forholding at least one unit of a biological fluid such as PC, in fluidcommunication with a pooling assembly 21. In the illustrated embodiment,the pooling assembly 21 includes a network or plurality of conduits 40that converge into a single conduit 60 at outlet or junction 50. Some ofthe conduits 40 function as inlets from the source containers. 20.Alternatively, pooling assembly 21 may include a housing having at leasttwo inlets and an outlet. The outlet or junction 50 of the poolingassembly 21 is in fluid communication with a receiving or transfercontainer 22. In the illustrated embodiment, fluid communication withthe receiving container 22 is preferably established by a conduit 60.Interposed in the conduit 60 between the outlet or junction 50 and thecontainer 22 may be at least one device or assembly. For example, asshown in the illustrated embodiment, the manifold assembly 100 mayinclude a gas inlet 30, a drip chamber 31, a leucocyte depletionassembly 32, and a gas outlet 33.

Each of the components of the invention will now be described in moredetail below.

The source and receiving containers which are used in the biologicalfluid processing assembly may be constructed of any material compatiblewith biological fluids. A wide variety of these containers are alreadyknown in the art. For example, blood collection and satellite bags aretypically made from plasticized PVC, e.g. PVC plasticized withdioctylphthalate, diethylhexylphthalate, or trioctyltrimellitate. Thebags may also be formed from a polyolefin, polyurethane, polyester, or apolycarbonate.

The pooling assembly of the instant invention provides fluidcommunication between at least two source containers and a receivingcontainer, preferably by channeling multiple flow paths into a singleflow path. As illustrated in the Figure, the pooling assembly 21preferably comprises a plurality of conduits 40 and an outlet orjunction 50. Although the conduits can be configured in a number ofways, the pooling assembly preferably comprises a network or tieredarrangement of conduits 40, preferably including one or more Junctions,such as one or more Y-connectors. As used herein, the conduits providefluid communication between the source of the biological fluid, such asseparate unit containers 20, and a multiple unit container, such astransfer or receiving container 22. A clamp, seal, valve, transfer legclosure, or the like, may be located within or on at least one of theconduits.

Alternatively, the pooling assembly 21 may include at least one devicehaving multiple inlets and a single outlet in fluid communication withjunction 50.

The pooling assembly used in the instant invention may be constructed ofany material compatible with a biological fluid. For example, thepooling assembly may be composed of a non-flexible material, forexample, acrylonitrile butadiene styrene (ABS), polycarbonate, orstainless steel. Alternatively, it may be composed of a flexiblematerial, such as polyvinyl chloride (PVC), or plasticized PVC, e.g.,PVC plasticized with dioctylphthalate, diethylhexylphthalate, ortrioctyltrimellitate.

In accordance with another embodiment of the invention, the biologicalfluid processing system may include a drip chamber 31. As noted in moredetail below, drip chamber 31 may be used to prevent gas from reaching aleucocyte depletion assembly 32 and/or the receiving container 22downstream of the drip chamber, and for maximizing recovery of thebiological fluid.

The drip chambers which may be used in the biological fluid processingassembly may be constructed of any material compatible with biologicalfluid and gas. Furthermore, the drip chamber may include at least oneporous element, preferably a liquophobic porous membrane, that allowsgas into and/or out of a biological fluid processing system, but resiststhe passage of biological fluid. The porous element may be positioned ina conduit, or, more preferably, it may be included in a housing of thedrip chamber. Further, the surface of the element may be oriented in avariety of ways with respect to the flow of the biological fluid. Forexample, two porous elements may be placed at opposite ends or sides ofthe drip chamber, or a single element may be offset within the dripchamber.

The leucocyte depletion assembly 32 comprises at least one porous mediumwhich removes leucocytes from the biological fluid. Exemplary leucocytedepletion media for use with a biological fluid such as PC is disclosedin U.S. Pat. No. 4,880,548. The leucocyte depletion assembly 32 may bepositioned in the manifold assembly in a variety of ways. For example,it may be located downstream of the outlet of the pooling assembly 50and the drip chamber 31.

A plurality of leucocyte depletion assemblies may be used in connectionwith the pooling assembly of the instant invention. For example, aplurality of leucocyte depletion assemblies may placed in a plurality ofpooling assembly inlets, i.e., in direct communication with theindividual source containers of biological fluid. Alternatively, aplurality of leucocyte depletion assemblies may be placed moredownstream in the pooling assembly, i.e., at similar or different tiersof the pooling assembly. In a preferred embodiment, a leucocytedepletion assembly 32 is interposed between the source containers 20 andthe receiving container 22, for example, in conduit 60.

In another embodiment, a gas inlet and/or a gas outlet may be used tomaximize the recovery of biological fluid in receiving or transfercontainer 22. Preferably, the gas inlet 30 and the gas outlet 33 may be,respectively, upstream and downstream of the leucocyte depletionassembly 32. More preferably, as exemplified in the Figure, the gasinlet 30 is downstream of the outlet of the pooling assembly 50 andupstream of the drip chamber 31, which is upstream of the leucocytedepletion assembly 32, while the gas outlet 33 is downstream, interposedbetween the leucocyte depletion assembly 32 and the receiving ortransfer container 22. Alternatively, a gas inlet and/or a gas outletmay be positioned in a drip chamber, a conduit, or the receiving and/orsource containers.

The gas inlet is a porous element which allows gas into a biologicalfluid processing system. Thus, the gas inlet may provide for increasingthe recovery of a valuable biological fluid (e.g., PC) that mayotherwise be retained in various components of the manifold assemblyduring processing and would otherwise be lost.

The gas outlet is a porous element which allows gas that may be presentin a biological fluid processing system out of the system. Thus, the gasoutlet may provide for minimizing the volume of gases that remain in, orin contact with, a biological fluid during processing. The gas outletmay also allow gas into the biological fluid processing system.

The gas inlet and gas outlet should be chosen so that the sterility ofthe system is not compromised.

The gas inlet and gas outlet each comprise at least one porous elementdesigned to allow gas to pass therethrough. A variety of materials maybe used, provided the requisite properties of the porous element areachieved. These properties include the necessary strength to handle thedifferential pressures encountered in use and the ability to provide thedesired filtration capability while providing the desired permeabilitywithout the application of excessive pressure. In a closed system, theporous elements of the gas inlet and the gas outlet should alsopreferably have a pore rating of about 0.2 micrometer or less topreclude bacteria entering the system.

Preferably, the gas inlet and gas outlet include at least oneliquophobic porous element. Because the liquophobic porous element isnot wettable, or poorly wettable, by the biological fluid beingprocessed in the system, gas in the system that contacts the liquophobicelement will pass through it, while the biological fluid will not. Thegas outlet may also include at least one liquophilic porous element,that allows gas to exit, but not enter, the system. In a preferredembodiment of the invention, the gas outlet includes both a liquophobicmembrane and a liquophilic membrane. Additionally, the gas inlet and/orthe gas outlet may be included in a housing, which may include a cap orclosure. Exemplary gas inlets and gas outlets and processes for usingthem are as disclosed in PCT/US91/03616, filed 24 May 1991.

As noted above, the placement of the gas inlet and/or the gas outlet maybe optimized to achieve a desired result. For example, the gas inlet 30may be located as far upstream of the manifold outlet or junction 50 asis practical in order to sufficiently maximize the recovery ofbiological fluid from the manifold assembly 100. Thus, gas inlets may belocated in each of the source containers 20 of the biological fluid tobe pooled. Alternatively, the gas inlet 30 may be placed in a conduit 40or downstream of the outlet or junction 50 of the pooling assembly 21.

Also, it may be desirable to locate the gas outlet 33 in conduit 60downstream of the outlet or junction 50 and as close to receiving ortransfer container 22 as is possible in order to maximize the volume ofgas that is removed from the manifold assembly 100. Alternatively, thegas outlet may be located in the receiving or transfer container 22itself. The gas inlet or the gas outlet may be located in the dripchamber 31. In a preferred embodiment of the invention, a gas inletand/or a gas outlet may be interposed between the source containers 20and the receiving container 22, for example, in conduit 60.

Included within the scope of the invention is the use of more than onegas inlet and/or gas outlet. For example, when the pooling assemblyassemblies, the pooling assembly may also include a plurality of gasinlets and/or gas outlets in any of the containers, or in any of theconduits communicating with the leucocyte depletion assemblies.

A method according to the invention may be described with reference tothe Figure, where the components are shown in a preferably verticalarrangement, with the source containers 20 at the highest point.Biological fluid, as used hereinafter, PC, in a plurality of containers20 passes through the conduits of the pooling assembly 21 and throughoutlet or junction 50 to receiving or transfer container 22. As the PCflows, it preferably contacts at least one device, assembly, or porouselement, e.g., a gas inlet 30, a drip chamber 31, or a gas outlet 33,for preventing gas from reaching a leucocyte depletion assembly or thereceiving container, and for maximizing the recovery of the PC, which isinterposed between the source containers 20 and the receiving ortransfer container 22. In accordance with the present invention, the PCmay also pass through at least one leucocyte depletion assembly 32 whichis interposed between the source containers 20 and the receiving ortransfer container 22.

In order to maximize recovery of PC prior to processing, air or gas maybe introduced into the source containers 20 through the gas inletassembly 30 or the gas outlet assembly 33, preferably by using a syringe(not shown). As used herein, air or gas refers to any gaseous fluid,such as sterilized air, oxygen, carbon dioxide, and the like; it isintended that the invention not be limited to the type of gas used.While the introduced fluid is preferably ambient air or a sterile gas,some non-gaseous fluids may also be suitable. For example, fluid that islighter than the biological fluid and is non-reactive with it isincluded within the scope of the present invention.

Introducing gas into the source containers 20 may be accomplished byopening a flow path from the gas inlet 30 or the gas outlet 33 to theappropriate source container 20, while closing the flow path to thereceiving or transfer container 22. For example, the clamps on theconduits leading to the receiving or transfer container 22 and all butone container 20 may be closed, so that when gas is introduced into thesystem, gas in the conduit will enter the open container. In a preferredembodiment, the process includes introducing gas sequentially into thesource containers 20. The flow path to each source container may beclosed after gas has been introduced into that container.

The flow path to the first source container 20 is then opened, and asthe PC passes from the first source container 20, and flows through thepooling assembly 21 toward receiving or transfer container 22, itdisplaces the gas that was ahead of the column of flowing PC; this gasis exhausted or removed from the system. The gas may be vented from thesystem through a porous element in the drip chamber or in the conduit,or preferably, through an open gas outlet 33. Once the gas has beenexhausted from the system, the gas outlet may be inactivated to preventgas from entering the system. For example, the gas outlet may beinactivated by manually closing the outlet, e.g., by capping orclamping. Preferably, the gas outlet includes a liquophobic element, andmore preferably, both a liquophobic element and a liquophilic element,which inactivates the outlet automatically, upon wetting by the PC.

Once the gas ahead of the PC column has been exhausted and the flow ofPC has stopped, clamps adjacent to the other source containers areopened, preferably, sequentially, so that PC from the other containers20 may pass through the pooling assembly 21 toward the receiving ortransfer container 22. The clamp adjacent to the receiving or transfercontainer 22 is opened so that the PC can flow into the container 22.Preferably, the clamp adjacent to the receiving or transfer container 22is opened before the clamps adjacent to the other source containers areopened.

Initiating the flow of PC from the other source containers alsodisplaces gas ahead of the other units of PC. Preferably, this gas maybe collected in drip chamber 31 interposed between the outlet orjunction 50 and the receiving or transfer container 22. Passing the PCthrough a drip chamber 31 may include collecting gas and/or controllingthe rate of flow of the PC. The drip chamber 31 is typically inverteduntil the PC fills the drip chamber, at which point the drip chamber isreturned to its normal orientation.

In accordance with the invention, the PC may also be passed through aleucocyte depletion assembly 32 interposed between the outlet orjunction 50 of the manifold assembly 21 and the receiving or transfercontainer 22. Preferably, the leucocyte depletion assembly 32 is locatedbetween the gas inlet 30 and the gas outlet 33. An exemplary process forpassing the PC through a leucocyte depletion assembly is disclosed inU.S. Pat. No. 4,880,548.

As the PC passes through the drip chamber 31 and the optional leucocytedepletion assembly 32, the gas ahead of the PC may be exhausted throughthe gas outlet 33 as described previously. Pooled PC is then recoveredin the receiving or transfer container 22 and, in accordance with theinvention, the introduction of air or gas into the receiving containeris eliminated Or minimized, so the PC is recovered without collectingair.

In order to maximize recovery of PC, gas may be introduced behind the PCretained in the system. The gas that was initially introduced into thesource containers 20 through either the gas inlet 30 or the gas outlet33 will follow the PC as it flows through the conduits. This increasesthe recovery of the PC, since the gas following the PC "chases" thefluid from the conduits. Furthermore, after the PC has passed throughthe pooling assembly into the receiving or transfer container 22 and thesource containers 20 have collapsed, gas may be introduced behind theretained PC by opening gas inlet 30. Additional PC may then be recoveredin the receiving or transfer container 22.

Once recovery of PC has been completed, receiving or transfer container22 may be sealed and separated from the system, without the introductionof air into the container. Preferably, receiving or transfer container22 is heat sealed, although other methods of sealing are also suitable.

Other variations are encompassed by the present invention. Thus, the gasoutlet may be used as a gas inlet, and, conversely, the gas inlet may beused as a gas outlet, at different stages of processing of the PC. Forexample, gas may be introduced and exhausted using a gas inlet and a gasoutlet as described above, and the PC is recovered in a receiving ortransfer container. Gas may then be introduced through the gas outlet,so that the PC remaining in the containers and/or held up in theleucocyte depletion assembly or assemblies may be collected. Of course,gas may also be introduced through the gas inlet for a similar effect.

Further embodiments are encompassed by the present invention. Forexample, in one embodiment, the manifold assembly 100 may comprise allof the components shown in the Figure, except for the leucocytedepletion assembly 32. Another embodiment of the invention may compriseall of the components shown in the Figure except for the gas inlet 30,the leucocyte depletion assembly 32, and the gas outlet 33. In thisvariation, the drip chamber 31 preferably includes a porous element forventing gas. Additionally, another embodiment of the invention mayinclude only a single porous element interposed between the outlet ofthe pooling assembly 50 and the receiving or transfer container 22,which allows gas to flow therethrough. In each of these embodiments gasahead of the flow of the PC and gas pockets moving along the conduitwith the flow of PC may be prevented from entering the receiving ortransfer container. Further, gas may be introduced behind the flow of PCto maximize recovery of the PC.

EXAMPLE Example 1

The pooling assembly used to perform this example utilized six units ofPC in individual 60 ml single-unit containers, and a 1500 ml storagecontainer, set up in a manner that generally corresponds to thatdescribed for the FIGURE. The manifold assembly is arranged generallyvertically, with the pooling assembly and the conduit to the receivingcontainer having a total length of about 24 inches. Clamps on theconduits adjacent to the six single-unit containers of PC were closed,as was the clamp on the conduit between the transfer container and thegas outlet. The leucocyte 15 depletion assembly was produced inaccordance with U.S. Pat. No. 4,880,548.

A 60 cc syringe was used to introduce air through the gas inlet and intothe source containers. The gas outlet was capped. The plunger of thesyringe was drawn back to the "60 cc" mark, the gas inlet was uncapped,and then the syringe was connected to the gas inlet. The clamp to thefirst single-unit container, which contained a unit of PC, was opened,and the plunger of the syringe was pushed forward about 5-10 cc, thusintroducing air into the first single-unit container. The clamp to thatfirst container was then closed. The same procedure was followed withrespect to the remaining five single-unit containers.

The syringe was then removed, the gas inlet was recapped, and the gasoutlet was uncapped. The clamp to the first container was then opened toallow the PC to flow from the first container, and the drip chamber wasinverted and squeezed to fill the chamber. The drip chamber was thenreturned to its normal orientation, and the PC flowed through the dripchamber and leucocyte depletion assembly, toward the transfer container.Air was exhausted through the opened gas outlet, until the PC contactedthe liquophobic membrane in the gas outlet.

At this point, flow stopped, the clamp on the conduit leading to thetransfer container was opened, and PC flowed into the transfercontainer.

The conduits to the other five containers were then opened sequentially,and the PC flowed out of these containers. The PC passed through thedrip chamber, where the air in the system elements leading to the fivecontainers was collected, and then the PC passed through the leucocytedepletion assembly. The flow stopped when the six containers of PC haddrained.

At this point, PC remained in the leucocyte depletion assembly, the dripchamber, and the conduit downstream of the gas inlet. To recover some ofthis PC, the gas inlet was then uncapped, and the PC remaining in thedrip chamber, conduits and half of the leucocyte depletion assemblydrained into the storage container.

While the invention has been described in some detail by way ofillustration and example, it should be understood that the invention issusceptible to various modifications and alternative forms, and is notrestricted to the specific embodiments set forth. It should beunderstood that these specific embodiments are not intended to limit theinvention but, on the contrary, the intention is to cover allmodifications, equivalents, and alternatives falling within the spiritand scope of the invention.

What is claimed is:
 1. A method for processing biological fluidcomprising:introducing gas through at least one downstream gas inletthrough a pooling assembly into a first one of a plurality of upstreamsource containers of biological fluid while preventing the flow of gasfrom the gas inlet into a receiving container for receiving thebiological fluid, wherein the gas inlet is interposed between theplurality of upstream source containers and the receiving container, andwherein the pooling assembly is interposed between the gas inlet and theplurality of upstream source containers; introducing gas through thedownstream gas inlet and through the pooling assembly into a second oneof the plurality of upstream source containers of biological fluid whilepreventing the flow of gas from the gas inlet into the receivingcontainer; passing the biological fluid from the first upstream sourcecontainer through the pooling assembly, and through a leukocytedepletion device to leukocyte deplete the fluid from the firstcontainer, wherein said leukocyte depletion device is interposed betweenthe gas inlet and the receiving container; passing the biological fluidfrom the second upstream source container through the pooling assembly,and through the leukocyte depletion device to leukocyte deplete thefluid from the second container; and, passing the leukocyte depletedbiological fluid into the receiving container.
 2. The method of claim 1wherein passing the leukocyte depleted fluid into the receivingcontainer includes exhausting gas ahead of the leukocyte depletedbiological fluid and minimizing the flow of gas into the receivingcontainer before passing the leukocyte depleted fluid into the receivingcontainer.
 3. The method of claim 2 wherein passing the leukocytedepleted fluid into the receiving container includes exhausting gasahead of the leukocyte depleted biological fluid before opening abiological fluid flow path between the leukocyte depletion device andthe receiving container and then passing the leukocyte depleted fluidinto the receiving container.
 4. The method of claim 2 whereinexhausting gas includes passing gas through a gas outlet.
 5. The methodof claim 2 further comprising introducing gas through the gas inlet andpassing additional leukocyte depleted biological fluid into thereceiving container.
 6. The method of claim 1 wherein biological fluidis processed in a closed sterile system.
 7. A method for processingbiological fluid comprising:introducing gas through at least onedownstream gas inlet into a plurality of upstream source containers ofbiological fluid while preventing the flow of gas from the gas inletinto a receiving container for receiving the biological fluid, whereinthe gas inlet is interposed between the plurality of upstream sourcecontainers and the receiving container; passing the biological fluidfrom the plurality of upstream source containers through a poolingassembly to the receiving container; exhausting gas ahead of thebiological fluid; and introducing gas through the gas inlet behind thebiological fluid to maximize recovery of the biological fluid in thereceiving container.
 8. The method of claim 7 wherein biological fluidis processed in a closed sterile system.
 9. The method of claim 7wherein introducing the gas into the plurality of source containersincludes passing gas through the downstream gas inlet through thepooling assembly, wherein said assembly is interposed between the inletand the source containers.
 10. The method of claim 9 includingintroducing gas into the plurality of source containers sequentially.11. A method for processing biological fluid comprising:introducing gasthrough a downstream gas inlet and through a pooling assembly into aplurality of upstream source containers of biological fluid whilepreventing the flow of gas from the gas inlet into a receivingcontainer, wherein the gas inlet is interposed between the plurality ofupstream source containers and the receiving container, and wherein thepooling assembly is interposed between the gas inlet and the pluralityof upstream source containers; and passing biological fluid from theplurality of upstream source containers through the pooling assembly anda leucocyte depletion assembly to the receiving container.
 12. Themethod of claim 11 wherein a drip chamber is interposed between the gasinlet and the leukocyte depletion device, and the method includespassing biological fluid from the pooling assembly through the dripchamber and the leucocyte depletion device to the receiving container.13. The method of claim 12 further comprising exhausting gas through agas outlet.
 14. The method of claim 13 wherein the gas outlet isinterposed between the leucocyte depletion device and the receivingcontainer.
 15. The method of claim 13 wherein the receiving containerincludes the gas outlet.
 16. The method of claim 11 wherein biologicalfluid is processed in a closed sterile system.
 17. A method forprocessing biological fluid comprising:introducing gas through adownstream gas inlet into a plurality of upstream source containers ofbiological fluid while preventing the flow of gas from the gas inletinto a receiving container, wherein the gas inlet is interposed betweenthe plurality of upstream source containers and the receiving container,and wherein the pooling assembly is interposed between the gas inlet andthe plurality of upstream source containers; passing the biologicalfluid from the plurality of upstream source containers through a poolingassembly and a leucocyte depletion assembly to the receiving container;exhausting gas ahead of the biological fluid; and introducing gas behindthe biological fluid to maximize recovery of the biological fluid in thereceiving container.